In today's environment, more and more devices are becoming battery powered, such as mobile phones, computers and even automobiles. Consequently, longer battery life is being demanded for all of these devices. One source of extended battery life has been the use of lithium ion based battery cells.
Lithium ion batteries are comprised of three major components, an anode 10, an electrolyte 20, and a cathode 30, as seen in FIG. 1. Currently, performance of the battery is limited by the cathode 30, which means that the gravimetric capacity (as measured in mAh/g) of the cathode 30 is significantly lower than that of the anode 10. In order for cathode technology to match the capacity of new anode materials, such as silicon, the cathode 30 must have a high capacity and be able to withstand high cycle rates. A significant amount of research is being focused on increasing the performance of cathodes 30 for high energy and high power applications.
The main cathode materials in today's lithium ion batteries are LiCoO2, LiMn2O4, and LiFePO4. Each class of materials has its own set of advantages and disadvantages, which make them each valuable to different applications. For example, LiCoO2 has revolutionized lithium ion batteries for portable electronics like laptops and cell phones, while cheaper materials like LiMn2O4 and LiFePO4 dominate the market for electric vehicles.
The main anode material in commercial lithium ion batteries is graphitized carbon. While alternative materials, such as silicon, provide much higher capacity, problems such as volume expansion and unstable solid electrolyte interphase reactions, need to be solved before commercialization is possible.
Any improvement which increases the capacity, rate capability, or stability of the cathode or anode will subsequently increase battery life and cycling rate. Therefore, a system and apparatus which enhances these characteristics of the electrode would be beneficial.